(1) Field of the Invention
This invention relates to a novel oil-modified resin suitable for use in printing inks. More specifically, this invention relates to a novel oil-modified resin from an acid-modified cyclopentadiene resin, an oily modifier and a polyvalent metal compound as a coupling agent.
This invention further relates to a process for preparing such an oil-modified resin, and to a printing ink composition containing such an oil-modified resin as a vehicle component.
(2) Discussion of the Prior Art
Various methods have been known heretofore about the modification of cyclopentadiene resins. For example, there have been known a method which comprises cooking a cyclopentadiene resin and a natural drying oil (U.S. Pat. No. 3,084,147), and a method which comprises reacting a cyclopentadiene resin with a higher unsaturated fatty acid in the presence of a metal compound (Japanese Patent Publication No. 2633/75) in order to use the resin as an ink vehicle. With these methods, however, the resins obtained do not have sufficient properties required of resins for printing inks, such as wettability with pigments, solubility in ink solvents, and viscosity characteristics, and are therefore unsuitable for use in inks.